Katie
If he wants time to "sort things out", then give him time to sort things out. If you send him a card, he may take it as being "clingy". Don't be clingy. Give him time and space, if that is what he asked for, he needs it.
I've been dealing with this for almost 2 years and the best thing I ever did was letting go. Letting go of contacting him, checking on him, asking him questions. This doesn't mean that you don't care or you don't love him anymore, it just means that you let him deal with this all by himself and you don't get involved. It helped ME heal.
Being able to just let go was hard and it took me a couple of months, but I'm glad I did and you know what, now he is starting to come around, again.
It is the hardest thing I've ever had to do in my life, especially after being married 25 years, but I'm glad I did.
I hope you find peace
Stillhoping